Driver-assistance systems are widespread in recent motor vehicles and are experiencing rapid development.
Adaptive cruise control (ACC) has been known for some time. Such an assistance mode automatically adjusts the speed in order to keep a constant safety distance from the vehicle in front of the user using information collected on this vehicle (in particular the distance and the approach speed) using one or several radar, lidar or infrared sensors.
Also known, in particular from US Published patent application US 2013/0096767, are dynamic lane departure warning systems. These are generally referred to using the acronyms ALKA (for “Active Lane Keep Assist”), LKAS (for “Lane Keep Assistance System”), ALA (for “Active Lane Assist”) or ALC (for “Active Lane Control”), and detect the lines marked out on the ground using sensors and/or optical cameras, and dynamically intervene on the vehicle when it deviates from its traffic lane. In such a scenario, the driver-assistance system will then automatically correct the direction of the vehicle and/or activate braking.
More recently, two completely autonomous driver-assistance modes have appeared in order to help the driver in dense traffic situations on divided highways where the vehicle's speed is reduced.
This is in particular the case for driver-assistance modes in traffic jams (better known under the acronym TJC for “Traffic Jam Chauffeur”) intended to relieve the driver in dense traffic or traffic jam situations (speeds below 50/70 km/h) on divided highways (highways and express roads).
In case of a degradation of the environmental driving context which would require a return to the manual driving mode, these TJC-type assistance modes are capable of maintaining fully automated guidance of the vehicle over a fairly long transitional period of around ten seconds before returning to the manual driving mode, such that the driver is not required to keep his eyes fixed on the road and can perform other tasks (placing telephone communications, watching a movie through the vehicle's entertainment system, playing a videogame on a computer or tablet, reading a book or magazine, etc.).
Lastly, driver-assistance modes have recently appeared on highways commonly referred to using the acronyms HAD (for “Highway Automated Driving”) or AHDA (for “Automatic Highway Driving Assist”). These driver-assistance modes are also able to relieve the driver on divided highways, but without usage restrictions relative to the speed of the vehicle or the density of the road traffic.
In such an embodiment, the fully automated guiding can only be maintained over a short transitional period (typically comprised between 1 and 3 seconds) in case of degradation of the driving context requiring a return to manual driving. It is therefore essential for the driver to maintain a certain attention level on the road at all times in order to be ready to take back control of the vehicle instantaneously.
Some vehicles are thus now provided with a driver-assistance system offering both of these last two complementary fully automated driving modes.
However, in such a scenario, the terms for implementing these two modes are made completely independent of one another: each may only be activated from a manual driving mode, without the possibility of transitioning between the two directly.